The invention relates to the field of gas turbine engines and to the field of power generation and to water reclamation; more particularly, it relates to method and apparatus for a gas turbine regenerative engine with exhaust gas water extraction.
Variations of Gas Turbines
There are many variations on simple cycle gas turbines. Each offers something special, be it operating economies or features that meet specific needs. The features might be small size, lightness in weight, high reliability, simplicity, or another measurable attribute. Emphasis is often placed on performance and power density, and achieving these objectives through use of known technologies and sound design principles for compressors, turbines, combustors, heat exchangers, and technology from related conventional materials sciences would be desirable. It is expected that achieving large gains requires the component arrangement to be new and different, to depart significantly from conventional designs. Any departure that results in an increase in complexity also has to significantly improve performance to be commercially useful; the more the departure, the more attractive the gains have to be.
Without question, component research and development efforts over recent years have served well to define advanced levels of aerodynamic and thermodynamic component efficiency. By combining these advances with similar gains in materials sciences and cooling technologies, capability now exists to design for high stage pressure ratios and high operating temperatures. But adopting an approach that would capture the full range of these advances would be very costly and would involve undesirably high risks. What is needed are the benefits to be derived from a new flow-path arrangement, rather than high stage loadings, high temperatures, and high stresses.
Fundamental Combustion Characteristics of Fuels
For most gaseous fuels, the products of complete combustion are carbon dioxide and water (in the form of water vapor). Depending on content, small amounts of sulphur dioxide can be produced, along with other gaseous products. However, the most significant products of combustion, by far, will be carbon dioxide and water. The rest, for the purpose of this discussion, can be ignored. The most important fundamental result is that for every pound of fuel burned, in combination with the ambient air used to support combustion, the gases produced will contain as much as 2.25 pounds of water vapor and up to 2.75 pounds of carbon dioxide. Until now, it does not appear that any attention has been given to recovering any of the products of this combustion, let alone recovery of the exhaust water. Fruitful human endeavors have always depended upon a readily available water supply. What is desirable, and what would be different from any other power producing system, is a power producing system from which exhaust gas water may readily be recovered. What is needed is a source of water that generates power efficiently, particularly in drought-ridden areas or desert regions; what is needed is an engine design for applications in developing regions that need two vital commodities: water and power. What is needed is a design that is independent of geographical location, climate, or changing meteorological conditions, but which does not have a negative impact on other engine favorable operating characteristics.
What is disclosed is an engine design for applications in developing regions that need two vital commodities: water and power.
The benefits disclosed herein are derived as follows:
A. First, only flow path arrangements that will enhance thermodynamic capability without depending on new, high-temperature technologies are considered. If high stage pressure ratios are not absolutely needed to achieve high cycle efficiency, then another way to get more power and better efficiency for the same size is to be employed.
B. Any special advantages to using heat exchangers such as regenerators or intercoolers in a new flow path are considered with a view toward achieving gains in efficiency (especially fuel saving) that outweigh any added complexity of incorporating the coolers into any new flow path.
C. Use of a bottoming cycle to augment output power is considered as well, especially as to whether it yields enough improvement, and how best to incorporate a bottoming cycle into the new system.
The resulting system disclosed is designed to fill a dual need; that is, provide a source of water while generating power efficiently. The flow path arrangement has been tailored to accomplish both. In that sense, the configuration is quite different from conventional through-flow designs; however, the components are well within known capabilities. The same is true for the heat exchangers (regenerators and coolers) and for elements of the bottoming cycle disclosed herein as well.
In simple terms, a bottoming cycle to increase thermodynamic efficiency, and a condensing unit to recover water from the products of combustion are preferably added to a basic but novel controlled feedback regenerative turbine engine, also referred to herein as the regenerative engine. The resulting configuration is unique in that it can deliver power efficiently while producing significant amounts of potable water, features that can be a priceless combination in drought-ridden areas or desert regions.
The core of the disclosed power/water system is the novel regenerative engine. This engine is based on well-established technologies related to successful turbine engines. But the novel regenerative engine differs from others in production in that the flow path is tailored to maximize efficiency and output power well beyond conventional practice. For example, fuel consumption rate of a disclosed regenerative engine is at least 10 percent lower than that of a conventional diesel engine, while specific power is roughly twice that of the most advanced turbine engine. The novel flow path for such an engine may be seen in FIG. 2.
An improved turbine engine topology is disclosed, wherein the improvement comprises a repositioning, with respect to a conventional intercooled regenerative turbine engine topology, of exhaust gas output from a low pressure turbine stage to a regenerator, to an exhaust gas output from a high pressure turbine stage to the regenerator. The engine topology may additionally employ, as an intermediate stage between the high pressure turbine and the low pressure turbine, a feedback control system, whereby the exhaust gas output from the high pressure turbine stage to the regenerator flows through the feedback control. The engine topology may advantageously also employ an additional cooler and an additional exhaust gas output in the feedback control, whereby exhaust gas flows from the feedback control through the additional cooler to a high pressure compressor stage, or the exhaust gas can flow from the feedback control through a bottoming cycle to the high pressure compressor stage. An exhaust gas condenser may advantageously be placed into the bottoming cycle system. The bottoming cycle/condenser improvements may alternatively be effected an other wise conventional intercooled regenerative turbine engine topology.